The combined roles of oxygen vacancy and electron doping in mediating local and nonlocal magnetic ordering of Fe doped in In 2 O 3 and Co doped in ZnO have been investigated within first-principles density functional theory. We first show theoretically that two magnetic dopants can be stabilized energetically around an oxygen vacancy, and are ferromagnetically coupled to form a local magnetic polaron.Furthermore, electron doping plays the elegant dual role of further enhancing the ferromagnetic stability of a local polaron, and more crucially, mediating the nonlocal 2 magnetic coupling between two polarons. We finally provide experimental evidence supporting these strong predictions.

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The 𝛾 ′ -Fe4N films on Cu underlayers are deposited on the glass and Si substrates by dc magnetron reactive sputtering. The effects of Cu underlayer on the structure, morphology and magnetic properties of the 𝛾 ′ -Fe4N films are studied. The single-phase 𝛾 ′ -Fe4N films with Cu underlayers on the glass substrate are obtained, while the mixture of Fe and 𝛾 ′ -Fe4N is observed on the Si substrate. In comparison with the films without Cu underlayers, the grains of the films with Cu underlayers exhibit a non-uniform size distribution and give rise to a rougher surface. The magnetic measurements indicate that the 𝛾 ′ -Fe4N films show a good soft ferromagnetic behavior. The enhanced coercivity in the films with Cu underlayers is observed due to the deterioration of the crystallographic structure as well as the rougher surface.

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